First result from the Double Chooz reactor-neutrino experiment

Abstract

We report first results of a search for the non-zero neutrino mixing angle \theta_{13} from the Double Chooz experiment. Double Chooz aims to measure the mixing angle based on anti-electron-neutrino disappearance as a consequence of neutrino oscillation. A new generation of anti-electron-neutrino detector having 10 m^3 fiducial volume is located 1 km from the two 4.25 GW_{th} reactors at the Chooz Power Plant in France. Physics data taking has been continuing since April 2011. A ratio of observed-to-predicted event rate of 0.944 +/- 0.016 (stat) +/- 0.040 (syst) was obtained in 101 days of detector running. Analyzing both the rate and their energy spectral shape, we found sin^{2}2\theta_{13} = 0.086 +/- 0.041 (stat) +/- 0.030 (syst) at \Delta m^2_{atm} = 2.4 x 10^{-3} eV^2.